Biomedical subjects

Freddy Haesebrouck

Publications and source records attributed to Freddy Haesebrouck.

At least 55 records · Page 3Linked to original sources

PubMed2005

Evaluation of tRNA gene PCR for identification of mollicutes.

We evaluated the applicability of tRNA gene PCR in combination with fluorescent capillary electrophoresis with an ABI310 genetic analyzer (Applied Biosystems, Calif.) for the identification of different mollicute species. A total of 103 strains and DNA extracts of 30 different species belonging to the genera Acholeplasma, Mycoplasma, and Ureaplasma were studied. Reproducible peak profiles were generated for all samples, except for one M. genitalium isolate, the three M. gallisepticum isolates, and 8 of the 24 Ureaplasma cultures, where no amplification could be obtained. Clustering revealed numerous discrepancies compared to the identifications that had been previously obtained by means of biochemical and serological tests. Final identification was obtained by 16S rRNA gene amplification followed by sequence analysis and/or restriction digestion. This confirmed the identification obtained by tRNA gene PCR in all cases. Seven samples yielded an unexpected tRNA gene PCR profile. Sequence analysis of the 16S rRNA genes showed that six of these samples were mixed and that one had a unique sequence that did not match any of the published sequences, pointing to the existence of a not-yet-described species. In conclusion, we found tRNA gene PCR to be a rapid and discriminatory method to correctly identify a large collection of different species of the class of Mollicutes and to recognize not-yet-described groups.

Acholeplasma↗

PubMed2005

Development of a gut perfusion model as an alternative to the use of live fish.

An alternative fish model with the principal aim of studying the interaction between fish pathogens and the intestinal tissue was developed. The preparation consisted of an excised gut tractus from rainbow trout (Oncorhynchus mykiss), perfused through cannulation of the aorta intestinalis ventralis with filtered and heparinized Cortland+dextran 1% as the perfusion fluid. This perfusion fluid was delivered by means of a drip. The perfused gut tractus was suspended in a circular bath filled with Ringer solution, which was aerated and kept at a constant temperature of 12 degrees C. Unperfused gut placed in Ringer solution at the same temperature served as the negative control. Perfusion was effective in maintaining the gut in a healthy condition for at least 60 min with only slight oedema and sloughing of the epithelium. Conversely, the unperfused gut revealed excessive tissue degeneration and severe necrosis.

Animals↗

PubMed2004

Protection of laying hens against Salmonella Enteritidis by immunization with type 1 fimbriae.

Eighteen chickens were immunized subcutaneously with purified type 1 fimbriae from Salmonella enterica serotype Enteritidis at 18 and 21 weeks of age. Evidence of IgG and IgA responses was found in the eggs and in the sera of the immunized hens. Three weeks later, immunized and non-immunized chickens (n=18) were challenged intravenously with 2x10(7) live Salmonella enterica serotype Enteritidis. There was no significant difference in the numbers of eggs laid by immunized and non-immunized birds. The percentage of Salmonella contaminated eggs was significantly higher in the non-immunized group than in the immunized group due to a higher percentage of contamination of the externally disinfected egg shells. There were no statistical differences in the percentages of contaminated yolks and egg whites between control and immunized birds. No differences in the number of colonizing bacteria could be found in the spleen nor in the liver between the immunized and the control groups throughout the experiment. Salmonella was cleared from the ovary of the immunized birds in the second week p.i., in contrast to the control birds where Salmonella was isolated till the third week after infection. Oviducts were significantly more infected in the control group than in the immunized group. Salmonella was cleared from the oviducts at 3 weeks p.i. in the immunized hens but not in the control hens. In conclusion, we demonstrated that the immunization of laying hens with type 1 fimbriae reduced the number of contaminated eggs and reduced the colonization of the reproductive organs.

Animals↗

PubMed2004

Quantification of the spread of Mycoplasma hyopneumoniae in nursery pigs using transmission experiments.

Mycoplasma hyopneumoniae (M. hyopneumoniae) is present in almost all swine herds worldwide, but transmission of the pathogen through herds is not yet fully clarified. The aim of this study, performed in 2003, was to investigate and to quantify the transmission of M. hyopneumoniae under experimental conditions by means of an adjusted reproduction ratio (Rn). This Rn-value, calculated according to the final size method, expresses the mean number of secondary infections due to one typical infectious piglet during the nursery period. The period lasted from 4 to 10 weeks of age, corresponding with the nursery period used in most European production systems. Additionally, a comparison was made between transmissions of highly virulent and low virulent isolates. Forty-eight weaned piglets, free of M. hyopneumoniae, were housed in six separate pens. During 6 weeks, two animals experimentally infected with M. hyopneumoniae were housed together with six susceptible piglets. At the end of the study, the number of contact-infected animals was determined by the use of nPCR on bronchoalveolar lavage fluid. The Rn-values of the highly virulent and the low virulent isolates were estimated to be 1.47 (0.68-5.38) and 0.85 (0.33-3.39), respectively. No significant difference between the groups was found (P=0.53). The overall Rn was estimated to be 1.16 (0.94-4.08). Under the present experimental conditions, the transmission of M. hyopneumoniae, assessed for the first time by a reproduction ratio, shows that one piglet infected before weaning will infect on average one penmate during the nursery phase.

Animals↗

PubMed2004

Genotypic and phenotypic screening of high and low virulence Staphylococcus aureus isolates from rabbits for biofilm formation and MSCRAMMs.

At rabbit flock level, two types of Staphylococcus aureus infections can be distinguished. In the first type, caused by low virulence strains, the infection remains limited to a small number of animals. The second type of infection is caused by the high virulence strains, which spread throughout the rabbitry. The pathogenetic capacity of a particular S. aureus strain is attributed to a combination of extracellular factors and invasive properties such as adherence and biofilm formation. Twenty eight high virulence and 34 low virulence S. aureus isolates recovered from rabbits between 1998 and 2003 were used to study slime production on Congo red Agar (CRA) and prevalence of bap, icaA and icaD associated with biofilm formation. Furthermore these strains were screened for the presence of bbp, clfA, clfB, cna, ebpS, eno, fnbA, fnbB and fib encoding microbial surface components recognizing adhesive matrix molecules (MSCRAMMs). The presence of icaA and icaD was not correlated with slime production on CRA. Bap was absent in all strains. All rabbit S. aureus strains harboured clfA and clfB. The prevalences of ebpS, eno, fnbA and fib did not reveal striking differences between high and low virulence strains. FnbB prevalence in high virulence isolates was lower than in low virulence isolates and cna was absent in high virulence strains. It was remarkable that only high virulence strains were positive for bbp. Further research is necessary to elucidate the significance of bbp in the pathogenesis of high virulence strains.

Adhesins, Bacterial↗

PubMed2004

Antimicrobial resistance and resistance genes in Staphylococcus aureus strains from rabbits.

Fifty-six Staphylococcus aureus isolates recovered between 1998 and 2003 from 31 rabbit farms with and without problems of chronic staphylococcosis, were screened for resistance to enrofloxacin, erythromycin, gentamicin, lincomycin, neomycin, penicillin and tetracyclines using the agar dilution test. For penicillin, a disk diffusion test was also performed. The detection of tetP(B), tet(K), tet(L), tet(M), tet(O), tet(T), tet(W), erm(A), erm(B), erm(C) and mec(A) genes was done via a PCR assay. Four isolates showed resistance to erythromycin and lincomycin. These isolates were positive for the erm(C) gene in the PCR. Eleven strains were resistant to tetracyclines and all harboured the tet(K) gene. In the agar dilution test, five isolates showed resistance to penicillin, whereas in the disk diffusion test 12 isolates showed resistance. None of these 12 resistant isolates carried the mec(A) gene. Only one strain showed resistance to gentamicin, and all strains were susceptible to enrofloxacin and neomycin. This study demonstrates that resistance to antimicrobial agents in S. aureus isolates originating from rabbits is relatively rare compared to resistance in S. aureus isolates originating from other animals and humans.

Animals↗

PubMed2004

Efficacy of vaccines against bacterial diseases in swine: what can we expect?

This paper discusses what can be expected with regard to efficacy of antibacterial vaccines used in swine, based on the present knowledge of pathogen-host interactions. First, vaccination against bacteria that mainly cause disease by production of exotoxins is considered. Vaccines containing the inactivated toxin or a non-toxic but antigenic recombinant protein derived from the exotoxin can be expected to provide protection against disease. The degree of protection induced by such vaccines varies, however, depending amongst other things on the pathogenesis of the disease. Vaccination against clostridial infections, Actinobacillus pleuropneumoniae infections, progressive atrophic rhinitis and enterotoxigenic Escherichia coli, is considered. The second part of the article deals with vaccination against extracellular bacteria. Protection against these bacteria is generally mediated by antibodies against their surface antigens and certain secreted antigens, but cellular immunity may also play a role. Efficacy of vaccines against swine erysipelas, Streptococcus suis infections, Mycoplasma hyopneumoniae infections and swine dysentery is discussed. Finally, vaccination against facultatively intracellular bacteria is considered. For protection against these bacteria cell-mediated immunity plays an important role, but antibodies may also be involved. It is generally accepted that live-attenuated vaccines are more suitable for induction of cell-mediated immunity than inactivated vaccines, although this also depends on the adjuvant used in the vaccine. As an example, vaccination against Salmonella enterica serotype Typhimurium is discussed.

Animals↗

PubMed2004

tRNA-intergenic spacer PCR for the identification of Pasteurella and Mannheimia spp.

tRNA-intergenic spacer PCR (tDNA-PCR) was evaluated for its effectiveness in differentiating Pasteurella and Mannheimia (sub)species predominantly of ruminant origin. For this purpose, 38 reference strains and 13 field isolates belonging to both genera were investigated. tDNA-PCR enabled discrimination of all Pasteurella species tested (Pasteurella (P.) aerogenes, P. avium, P. canis, P. lymphangitidis, P. multocida, P. trehalosi). For the differentiation of the subspecies of P. multocida, an additional dulcitol reaction was required. Two of the five so far-defined Mannheimia species, M. granulomatis and M. varigena, had a distinct fingerprinting profile. The remaining three phylogenetically highly related species (M. haemolytica, M. glucosida, and M. ruminalis) clustered together. Nevertheless, M. ruminalis is non-haemolytic, and M. haemolytica and M. glucosida can be differentiated on the basis of two additional phenotypic characteristics (beta-glucosidase and aesculin hydrolysis). In conclusion, tDNA-PCR is a useful tool in differentiating organisms belonging to the genera Pasteurella and Mannheimia.

Animals↗

PubMed2004

Oropharyngeal carriage of macrolide-resistant viridans group streptococci: a prevalence study among healthy adults in Belgium.

OBJECTIVES: Viridans group streptococci (VGS) are gaining significance as reservoirs of resistance determinants for respiratory tract pathogens. Our aim was to investigate healthy adults for oropharyngeal carriage of VGS that are resistant to macrolides, as well as to other common antibiotics. METHODS: Macrolide-resistant VGS were isolated from throat samples of 154 healthy Belgian adults, and phenotyped and genotyped for erm(A), erm(B) and mef(A). In vitro susceptibilities to 10 antimicrobials and the presence of tetracycline resistance genes were also determined. RESULTS: Carriage was detected in 71% of the population screened, from whom 157 unique, macrolide-resistant VGS were isolated. A constitutive (cMLS) phenotype was present in 105 isolates, of which 102 isolates carried either erm(B) or erm(B) + mef(A). The remaining three isolates did not present with any of the genes studied. All 45 isolates showing the M phenotype carried mef(A). The least abundant inducible (iMLS) isolates (n = 7) carried either erm(B) or erm(B) + mef(A). The most abundant macrolide-resistant VGS species was Streptococcus mitis (51%). Co-resistance to tetracycline was identified in 114 isolates, of which tet(M) was present in 105, tet(O) in two and both tet(M) and tet(O) in one, while the remaining six isolates did not present with either gene. tet(M) was also present in four tetracycline susceptible and two intermediately resistant isolates. Fluoroquinolone resistance (ciprofloxacin MIC > or = 4 mg/L) was detected in 16 isolates. Resistance to telithromycin, penicillin and chloramphenicol was appreciably low. CONCLUSIONS: This study highlights a high oropharyngeal carriage of macrolide-resistant VGS and its co-resistance to tetracycline and fluoroquinolones among healthy Belgian adults.

Adolescent↗

PubMed2004

Clostridium perfringens in poultry: an emerging threat for animal and public health.

The incidence of Clostridium perfringens-associated necrotic enteritis in poultry has increased in countries that stopped using antibiotic growth promoters. Necrotic enteritis and the subclinical form of C. perfringens infection in poultry are caused by C. perfringens type A, producing the alpha toxin, and to a lesser extent type C, producing both alpha toxin and beta toxin. Some strains of C. perfringens type A produce an enterotoxin at the moment of sporulation and are responsible for foodborne disease in humans. The mechanisms of colonization of the avian small intestinal tract and the factors involved in toxin production are largely unknown. It is generally accepted, however, that predisposing factors are required for these bacteria to colonize and cause disease in poultry. The best known predisposing factor is mucosal damage, caused by coccidiosis. Diets with high levels of indigestible, water-soluble non-starch polysaccharides, known to increase the viscosity of the intestinal contents, also predispose to necrotic enteritis. Standardized models are being developed for the reproduction of colonization of poultry by C. perfringens and the C. perfringens-associated necrotic enteritis. One such model is a combined infection with Eimeria species and C. perfringens. Few tools and strategies are available for prevention and control of C. perfringens in poultry. Vaccination against the pathogen and the use of probiotic and prebiotic products has been suggested, but are not available for practical use in the field at the present time. The most cost-effective control will probably be achieved by balancing the composition of the feed.

Animal Feed↗

PubMed2004

Effect of type 1 fimbriae of Salmonella enterica serotype Enteritidis on bacteraemia and reproductive tract infection in laying hens.

Research on the role of type 1 fimbriae of Salmonella enterica serotype Enteritidis in poultry to date has been focused on the intestinal phase of the infection. This study aimed to investigate the role of type 1 fimbriae in a systemic infection by intravenously inoculating chickens with a fimD mutant or its parent strain. The fimD mutant was present in the blood for 3 weeks after infection, while the wild type parent strain was cleared within the first 3 days. The fimD mutant was isolated at least as much as the parent strain from the liver and spleen for up to 3 weeks after inoculation. The wild type strain was cleared from the caeca in the second week, while the fimD mutant was isolated from the caeca for up to 3 weeks after infection. The ovaries were more heavily infected by the fimD mutant than by the wild-type strain. In the first and second week after inoculation, the oviducts were more frequently infected by the mutant strain. The eggs of birds infected with the fimD mutant were less frequently contaminated with Salmonella. The shells of the eggs were more frequently contaminated by the wild type strain than with the mutant strain. Thus, the absence of type 1 fimbriae prolongs bacteraemia, modifies reproductive tract infection and reduces egg shell contamination by Salmonella enterica serovar Enteritidis.

Animals↗

PubMed2004

Presence and mechanism of macrolide-lincosamide resistance in Enterococcus columbae strains belonging to the intestinal flora of pigeons.

Faecal samples from 50 pigeons all originating from different lofts were screened for the presence of macrolide and lincosamide (ML)-resistant isolates of Streptococcus gallolyticus and Enterococcus columbae by plating the samples onto selective media. Sixty-eight ML-resistant E. columbae strains were recovered from the faecal samples of 29 animals. Two of these samples also harboured ML-resistant S. gallolyticus strains. The erm(B) gene was detected in 58 E. columbae and in five S. gallolyticus isolates. Four of these E. columbae isolates also carried the mef(A) gene. Five E. columbae strains possessed the mef(A) gene in the absence of erm(B). On the basis of the sequence of the complete erm(B) gene, 10 E. columbae isolates clustered together in six groups. In two of these isolates, the erm(B) gene sequence was identical to that of S. gallolyticus strains, indicating that exchange of resistance genes might occur between pathogenic and non-pathogenic bacterial species belonging to the pigeon's intestinal flora.

Animals↗

PubMed2004

Antimicrobial susceptibility patterns of Arcobacter butzleri and Arcobacter cryaerophilus strains isolated from humans and broilers.

The MICs of five antimicrobial agents were determined by the agar dilution method for 98 Arcobacter butzleri and 28 Arcobacter cryaerophilus strains from humans, and poultry. With gentamicin, a MIC of 16 microg/ml was recorded for one A. butzleri strain isolated from poultry, whereas for the other strains MICs ranged from 0.25 to 4 microg/ml. With ciprofloxacin, a bimodal distribution of susceptibility levels was seen for human A. butzleri isolates (0.015-0.03 versus 0.12-0.25), whereas MICs for 65 of the 68 A. butzleri poultry strains ranged from 0.12 to 0.5 microg/ml and three strains from three different broilers were resistant with a MIC of 16 microg/ml. One A. cryaerophilus strain from poultry was resistant to erythromycin at a MIC of 128 microg/ml, whereas MICs for the other Arcobacter strains ranged from 2 to 32 microg/ml. No difference in susceptibility or resistance among the human and poultry strains tested was observed with doxycycline and nalidixic acid. The presence of acquired resistance to erythromycin and ciprofloxacin among poultry isolates is a matter of concern, because the two antimicrobials are generally prescribed as first-line drugs for the treatment of infections with Campylobacteraceae in humans.

Animals↗

PubMed2004

Assessment of virulence of pigeon isolates of Salmonella enterica subsp. enterica serovar typhimurium variant copenhagen for humans.

Salmonella enterica serovar Typhimurium variant Copenhagen was isolated from 5 of 152 (3.3%) feral pigeons from the city of Ghent (Belgium) and from 26 pooled fecal samples from 114 pigeon lofts (22.8%). These isolates belonged to phage type (PT) 99. Seven of the pigeon isolates were further compared in vitro to five human variant Copenhagen isolates, 2 isolates of PT 208, 1 isolate each of PT 120 and U302, and a nontypeable isolate. No differences in invasiveness in human intestinal epithelial Caco-2 cells were found. The human strains, however, were able to multiply significantly more inside human THP-1 macrophages than the pigeon strains. After inoculation of mice with a pigeon PT 99 strain, high numbers of Salmonella bacteria were shed with the feces, the internal organs were heavily colonized, and the animals showed severe clinical symptoms resulting in death. In conclusion, the less-pronounced ability of the pigeon variant Copenhagen strains to multiply inside human macrophages than human strains as well as the lack of human PT 99 isolates during 2002, despite the relatively high frequency of this PT in the pigeon population, suggest these strains to be of low virulence to humans. However, the high virulence for mice of the tested strain implies that rodents may act as reservoirs.

Animals↗

PubMed2004

Cats as a risk for transmission of antimicrobial drug-resistant Salmonella.

To determine whether cats were a risk for transmission of Salmonella to humans, we evaluated the excretion of Salmonella by pet cats. Rectal-swab specimens were taken from 278 healthy house cats, from 58 cats that died of disease, and from 35 group-housed cats. Group-housed cats were kept in one room with three cat trays and a common water and feed tray. Eighteen (51.4%) of 35 group-housed cats, 5 (8.6%) of 58 diseased cats (5/58), and 1 (0.36%) of 278 healthy house cats excreted Salmonella. Salmonella isolates were of serotypes Typhimurium, Enteritidis, Bovismorbificans and 4:i:-. Acquired antimicrobial resistance was found in serotype Typhimurium (resistance to ampicillin, chloramphenicol, and tetracycline; to ampicillin; and to chloramphenicol) and 4:i:- strains (resistance to ampicillin, chloramphenicol, sulfonamides, trimethoprim, and sulfamethoxazole/trimethoprim). Cats that excrete Salmonella can pose a public health hazard to people who are highly susceptible to Salmonella, such as children, the elderly, and immunocompromised persons.

Animals↗

PubMed2003

Adhesion of high and low virulence Flavobacterium psychrophilum strains to isolated gill arches of rainbow trout Oncorhynchus mykiss.

The ability of Flavobacterium psychrophilum to adhere to the gill tissue of rainbow trout Oncorhynchus mykiss was evaluated. A gill perfusion model was adopted, offering a number of advantages compared to other in vitro as well as in vivo models. A comparison between the adhesion capacity of a high and low virulence F. psychrophilum strain was made. Experiments were additionally carried out to assess the influence of water quality (organic material, nitrite) and temperature on the adhesion process of the bacterial cells. The high virulence strain attached more readily to the gill tissue than did the low virulence strain. Moreover, the adherence of the high virulence strain of F. psychrophilum was influenced by a number of factors. These were immersion of the gill arches in water to which organic material or nitrite were added, and elevated temperature. The former 2 increased the adhesion ability, while the latter had a negative influence on the adherence process.

Animals↗

PubMed2003

Adhesion of Salmonella enterica serotype Enteritidis isolates to chicken isthmal glandular secretions.

The ability of Salmonella enterica serotype Enteritidis isolates to adhere to immobilized secretions of the isthmus of the laying hen was determined in an ELISA-type assay. One-third of the 56 isolates tested in the logarithmic growth phase, adhered to the isthmal secretions. Using a binding assay of the isolates to thin paraffin sections of the oviduct, we demonstrated that the receptor of the adhesion was localized inside the tubular gland cells of the isthmus. The adhesion to immobilized isthmal secretions as well as to the paraffin sections was blocked by the addition of mannose. A fimD mutant of S. Enteritidis, lacking type 1 fimbriae, did not adhere, confirming that the adhesion was mediated by type 1 fimbriae. Mannosylated glycoproteins were demonstrated in the isthmus glandular cells using confocal laser scanning microscopy by FITC-labelled Lens culinaris lectins. It is hypothesized that the binding of S. Enteritidis to isthmal secretions could play a role in the contamination of eggs through incorporation of the bacteria in the shell membranes.

Animals↗

PubMed2003

Lactobacillus ingluviei sp. nov., isolated from the intestinal tract of pigeons.

Lactic acid bacteria were isolated from the crop and intestines of pigeons. One group of strains, showing similar genomic patterns after screening with tRNA intergenic spacer PCR, could not be identified to the species level. Sequencing of the 16S rRNA gene of one representative strain revealed about 96% similarity to sequences from Lactobacillus fermentum and Lactobacillus mucosae. Determination of the DNA base composition, DNA-DNA hybridization experiments, SDS-PAGE of whole-cell proteins and biochemical testing confirmed that the seven strains studied constitute a single novel Lactobacillus species, for which the name Lactobacillus ingluviei sp. nov. is proposed. The type strain is strain KR3T (=LMG 20380T =CCUG 45722T).

Animals↗